Surface kelp fixes CO₂ into biomass by logistic growth toward a light/nutrient-limited carrying capacity:
dB/dt = r·B·(1 − B/K)
Periodically the raft is harvested and pressed into ballasted bundles that sink through the water column. Whether that fixed carbon counts as removal depends on how much organic matter survives the trip — governed by the Martin curve, the same power law oceanographers use for the biological carbon pump's particle flux:
F(z) = F(z₀)·(z / z₀)^(−b), z₀ ≈ 100 m
A larger exponent b (warmer water, more bacteria and oxygen) remineralizes organic carbon faster with depth, releasing CO₂ back into the water before it reaches the deep ocean. Heavier ballast sinks bundles through the shallow, bacteria-rich layer faster, giving remineralization less time to act before the sequestration horizon (≈1000 m, shaded band) is crossed — below which carbon is effectively isolated from the atmosphere for centuries by slow ocean mixing.
- Growth rate — sets how fast the raft's biomass (and CO₂ drawn into it) accumulates.
- Harvest interval — how often grown biomass is cut and dropped as a sinking bundle.
- Ballast weight — sink speed; faster sinking means less exposure time to shallow remineralization.
- Remineralization intensity — the Martin exponent b; higher values return more carbon to the water before it reaches depth.
Mass is converted from carbon to CO₂ using the 44/12 stoichiometric ratio (mass of CO₂ per mass of C).